Conventionally, in Long Term Evolution (LTE), when user equipment (UE) is configured with discontinuous reception, there are quite several timers need be configured to make the discontinuous reception work. The timers associated with DRX may be collectively referred to as DRX timers and may include, for example, onDurationTimer, drx-InactivityTimer, drx-RetransmissionTimer, and so on. In LTE, time units for all the DRX timers are the same as the scheduling unit, that is, a subframe or a Transmission Time Interval (TTI) having a time length of 1 ms.
In the next generation network, for instance, in New Radio (NR), the UE needs to support DRX as well and quite probably uses a DRX mechanism similar as in LTE. In other words, there may be quite several DRX timers need be configured to make DRX work in NR. Different from LTE, NR needs support different numerologies and/or TTI lengths. The absolute time durations of different numerologies/TTI lengths are different. By way of example, for a numerology of 15 kHz sub-carrier spacing (SCS), the corresponding TTI length is 1 ms. For a numerology of 30 kHz SCS, its TTI length is 0.5 ms.
For NR, a TTI may have a shorter transmission duration which comprises less Orthogonal Frequency Division Multiplexing (OFDM) symbols than a normal TTI comprising 14 OFDM symbols. For instance, a UE may be configured to be scheduled in slots comprising 7 OFDM symbols instead of in a normal TTI comprising 14 OFDM symbols. An even shorter slot may be used as well, for example, a mini-slot including 2 OFDM symbols.
If the DRX timer in NR is configured in the same way as in LTE, i.e. the time unit for all timers is set according to the same TTI length, it would cause some confusion. More specifically, since the scheduling unit for the numerology of 15 kHz is 1 ms while the scheduling unit for the numerology of 30 kHz is 0.5 ms, if a DRX timer has a value of 5, it indicates 5 ms for a numerology of 15 kHz but indicates 2.5 ms for a numerology of 30 kHz. In such case, the UE may be unclear about the time interval actually indicated by the DRX timer, when the DRX timer should be active, or when the DRX timer should be sleep. This would cause a mismatching issue between the network (NW) side and the UE. For example, the UE may miss the scheduling from the NW when it is sleeping but the NW thinks it is active, or may waste its power when it is actually active but the NW thinks it is sleeping. As such, transmission efficiency and network performance would be reduced.